Conventional marine pleasure craft and recreational vehicles have self-contained bathrooms and sewage storage systems which conduct their waste water to larger holding tanks in RV parks, dock facilities and other similar places. There are available pre-portioned chemical powders which are to be used by adding them directly into the holding tanks of the vehicles to thus sanitize and deodorize them. In the case of recreational vehicles for example, every time the vehicle is taken out and used, one of these pre-portioned doses of chemicals is added to the holding tank, and of course, is flushed out of the holding tank along with the waste when the tank is dumped.
This system of having chemicals introduced into the holding tank has certain disadvantages. First, an entire measure of the sanitizing chemicals must be used every time a vehicle is taken out and the tank subsequently dumped. Thus, even though the outing may only be for a day of two, the same amount of chemicals is used to sanitize the tank as would be necessary for a more extended trip when the entire tank is filled.
Additionally, besides the expense of requiring more chemical than is really needed, there is the nuisance of having to put the chemical in the tank, and the possibility that one might forget to add the chemicals, causing a fouling of the interior of the holding tank. Prior art tanks are provided with required anti-back-flow safety provisions to prevent the chemicals from moving upstream in the system and entering the fresh water tank. The anti-back-flow protection also prevents waste water from the toilet from entering, and then moving up through, the fresh water inlet. However, in some cases it is questionable whether these systems are effective. This is especially true in the common situation in which additive chemicals are downstream of the fresh water supply but are maintained at the same presssure, being upstream of the toilet flush valve. Since there is no steep pressure gradient to overcome, irrespective of check valves and other safety precautions there is a heightened possibility of system failure and chemical back-flow.
There is a need, therefore, for a simple, add-on unit which is readily connectable to existing systems to automatically treat incoming flushing water as it is dumped into the holding tank, so that pre-measure doses, added as water is used, sanitizes both the toilet and the holding tank, and lasts for many uses, without requiring any action of thinking on the part of the RV owners.